1. Field of the Invention
The present invention relates to seating load detection of a seat, which fixes members for supporting a seat cushion and a seat back on a floor by positioning members. More particularly, the present invention relates to seating load detection of a seat arranged in a vehicle without being limited thereto.
2. Description of the Related Art
For example, when an air bag to protect a passenger who is seated in a seat is provided in a vehicle, a seating load detecting device is attached to the seat of the vehicle in order to detect whether or not a passenger is seated in that seat, or in order to properly adjust a gas generating amount for blowing out the air bag according to the passenger""s weight. Japanese Patent Application Laid-Open No. HEI 11-1153 discloses an embodiment in which a load cell is disposed between a rail, which slidably guides a vehicle seat in the backward and forward direction of vehicle advancement, and a mount bracket which fixedly supports the rail to the vehicle floor, so as to detect the seat weight with this load cell. Japanese Patent Application Laid-Open No. HEI 11-1154 discloses a passenger detecting device in which a link assembly for measuring a seat cushion weight is interposed between a frame for supporting a seat cushion and the seat cushion, such that the seat cushion load is applied to a load cell by rotation of the link using a supporting point. Further, Japanese Patent Application Laid-Open No. HEI 11-94637 discloses a passenger detecting device in which a link assembly for measuring a seat cushion weight is interposed between a slide rail to be guided by a rail fixed to the vehicle floor and a seat cushion, such that the seat cushion load is applied to the load cell by rotation of the link using a supporting point.
With respect to the weight measuring mechanism in the above mentioned Japanese Patent Application Laid-Open No. HEI 11-1153, the load cell is mounted on the mount bracket and the guide real is further mounted on the load cell. Therefore, it appears easy to obtain such a mechanism; however, the realization thereof is in fact difficult. The vehicle seat must be strongly fixed to the vehicle floor and interposing a load cell between the mount bracket and the guide rail greatly reduces the seat supporting strength in both the vertical and horizontal directions. The mount bracket is designed differently for different types of vehicles such that the vehicle seat can be commonly used in a wide variety of vehicles. In this case, load cell standards and installation must be adjusted for each type of vehicle, which makes it difficult to lower the cost of the weight measuring device.
With respect to the weight measuring mechanism disclosed in the above mentioned Japanese Patent Application Laid-Open No. HEI 11-1154 and Japanese Patent Application Laid-Open No. HEI 11-94637, since the seat cushion is supported by a link mechanism for measuring the weight, the seat cushion can move vertically by a corresponding amount. Therefore, the seat cushion loses its inherent rigidity which is an important feature of a vehicle seat. Since the link mechanism is complicated and occupies a large space, the design of the vehicle seat must be largely modified. In the above mentioned Laid-Open Patent Publication No. HEI 11-94637, the link mechanism reacts individually in response to a front load and a back load of the seat cushion, so that it is impossible to detect the mass which escapes to the seat back. As a result, superior accuracy of detection cannot be expected.
In view of the foregoing problems, it is an object of the present invention is to provide a seating load detecting device, which is capable of being provided to a seat without greatly changing the original shape of the seat, improve the stability and the accuracy in seating load detection, and prevent deterioration of seat stability and comfort with the incorporation of a load detecting mechanism.
A seating load detecting device according to a first aspect of the present invention comprises a bracket for coupling a seating load supporting member to support a seat cushion and a seat back with a positioning member to position the seat on a floor, which elastically transmits the load applied on the seating load supporting member to the positioning member. The bracket is provided with a curved portion having opposing portions between the positioning member and the seating load supporting member. The bracket connects the seating load supporting member and the positioning member with a connecting portion extending vertically from the opposing portions, and is further provided with a load sensor at those opposing portions. Accordingly, distortion is generated in the bracket by a load on the seating load supporting member. However, since this distorts the shape of the bracket only slightly, the mechanism does not move substantially. The bracket only needs to be large enough to couple the seating load supporting member with the positioning member, with space for arranging a load sensor. Accordingly, it is not necessary to modify the original shape of the seat. Since the load sensor is disposed on the bracket and there is no movement mechanism such as a link for measuring weight, it is possible to improve the stability and the accuracy of the seating load detection, while maintaining the stability and comfort of the seat.
The curved portion has a spring function due to its rigidity. When a person sits on the seat cushion, the curved portion deforms such that the opposing portions of the curved portion become closer together. The load sensor responds to this change in the shape of the opposing portions. Since the curved portion easily expands and contracts in response to the load, the stability and the accuracy in the seating load detection is high. Further, since the displacement of the curved portion is a spring displacement, stability and comfort of the seat is not lost.
According to the foregoing aspect of the present invention, the shape of the curved portion is either generally U-shaped or V-shaped, such that the space between opposing portions within the curved portion narrows as the amount of the seating load increases.
Further, according to the foregoing aspect of the present invention, the space between opposing portions within the curved portion is adjusted so as to become narrower by applying a pre-load in the vertical direction.
According to this arrangement, it becomes possible to decrease the rigidity of the curved portion and increase the sensitivity of the seating load detection. Due to the seating load, the space between the opposing portions of the curved portion becomes narrow. Therefore, the stroke, i.e., the space between opposing portions, from a point where the opposing portions narrows by applying the seating load to a point where the end of the opposing portions contact each other, becomes short and the relatively light load allows the opposite portion""s edges to contact each other. As a result, a large distortion is not applied to the portion, which is provided with the load sensor, so that damage to or distortion of the bracket or the load sensor can be prevented.
A seating load detecting device according to a second aspect comprises a bracket for coupling a seating load supporting member to support a seat cushion and a seat back with a positioning member to position a seat on a floor to elastically transmit the load applied on the seating load supporting member to the positioning member. The bracket is provided with a load sensor. A limiting member which limits the moving amount in the vertical direction of the seating load supporting member when the load acts on the seating load supporting member is provided between the bracket or the seating load supporting member and the positioning member.
The application of excessive impact changes the shape of the curved portion or the bracket. According to this change of shape, the posture of the seat loses its figure. The above limiting member allows the amount for the shape change of the bracket to remain under a predetermined amount.
According to the second aspect, the limiting member is provided with a long hole in the vertical direction. The limiting member is fixed on any one side of the seating load supporting member or the positioning member and a protrusion which is movable within the long hole is provided on the other side, so that the vertical movement of the seating load supporting member is limited by a long hole.
According to the first and second aspects, the load sensor comprises a distortion gage. Accordingly, the bracket only needs to be large enough to couple the seating load supporting member with the positioning member and space for attaching a distortion gage, so it is not necessary to change the original shape of the seat. Since the distortion gage is integrated with the bracket and there is no movement mechanism, it is possible to improve the stability and accuracy of the seating load, while maintaining the stability and comfort of the seat. The curved portion has a spring function due to its rigidity. When a person sits on the seat cushion, the curved portion changes so that the opposing portions of the curved portion become close to each other and the distortion gage responds to the distortion of the opposing portions.
The object and the features of the present invention will become clear according to the description of the following embodiments with reference to the drawings.